U.S. patent number 7,517,157 [Application Number 11/936,839] was granted by the patent office on 2009-04-14 for all-plastic optical mini-connector.
This patent grant is currently assigned to The Boeing Company. Invention is credited to John V. Alexander, Rick Bomber, Michael R. McNiece, James L. Melquist, Robert A. Nowak.
United States Patent |
7,517,157 |
McNiece , et al. |
April 14, 2009 |
All-plastic optical mini-connector
Abstract
An optical fiber connector has a center component provided with
opposite first and second ends into which first and second
connector inserts holding ends of respective optical fiber bundles
are to be inserted, an optical core element mounted in the center
component having opposite ends against which the ends of the
respective optical fiber bundles in the first and second connector
inserts are to be abutted in alignment, and fastener elements
provided with the first and second ends for securely holding the
first and second connector inserts in abutting contact with the
respective opposite ends of the optical core element.
Inventors: |
McNiece; Michael R.
(Scottsdale, AZ), Alexander; John V. (Mesa, AZ), Nowak;
Robert A. (Mesa, AZ), Bomber; Rick (San Jose, CA),
Melquist; James L. (Tempe, AZ) |
Assignee: |
The Boeing Company (Chicago,
IL)
|
Family
ID: |
40229578 |
Appl.
No.: |
11/936,839 |
Filed: |
November 8, 2007 |
Current U.S.
Class: |
385/60;
385/54 |
Current CPC
Class: |
G02B
6/403 (20130101); G02B 6/2808 (20130101) |
Current International
Class: |
G02B
6/38 (20060101); G02B 6/40 (20060101) |
Field of
Search: |
;385/60,74,58,105,54 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Font; Frank G
Assistant Examiner: Tavlykaev; Robert
Attorney, Agent or Firm: Ostrager Chong Flaherty &
Broitman P.C.
Claims
What is claimed is:
1. An optical fiber connector comprising: a first connector insert
for holding exposed ends of a bundle of optical fibers of a
specified number packed in a pre-determined packing pattern; a
second connector insert for holding similarly exposed ends of an
opposite bundle of optical fibers of the specified number packed in
the pre-determined packing pattern; a center connector component
having opposite first and second ends into which the first and
second connector inserts are respectively inserted; and fasteners
provided with the first and second ends for securely holding the
first and second connector inserts so that the optical fiber
bundles are in abutting contact with an optical core element in the
center connector component and substantially in alignment with each
other in order to obtain a high level of optical transmission and
uniform light distribution between the optical fiber bundles;
wherein the fiber ends of each optical fiber bundle are held in a
respective ferrule, the respective ferrules having a corresponding
hexagonal cross-sectional shape that matches a hexagonal inner
cross-section of the connector inserts so that each connector
insert has one of the ferrules sleeved into it in proper alignment;
and wherein the pre-determined packing pattern is a dense hexagonal
packing pattern.
2. An optical fiber connector according to claim 1, wherein said
connector evenly transmits light at an efficiency of about 65% or
better.
3. An optical fiber connector according to claim 1, wherein the
first connector insert, the second connector insert, the center
component, the fasteners and the ferrules are made from a molded
plastic material.
4. An optical fiber connector according to claim 1, wherein the
dense hexagonal packing pattern comprises 4 fiber ends on each hex
side.
5. An optical fiber connector according to claim 4, wherein the
dense hexagonal packing pattern results in the center connector
component having an outside diameter of 0.25 inch.
6. An optical fiber connector according to claim 1, wherein said
connector inserts have keyed ends that slot into complementarily
keyed ends of the center connector component for rotational
alignment of the optical fiber bundles.
7. An optical fiber connector according to claim 1, wherein said
fasteners are external fastener caps that thread onto the opposing
first and second ends of the center connector component.
8. An optical fiber connector according to claim 1, wherein the
optical core element of the center connector component is a glass
mixing rod.
9. An optical fiber connector according to claim 8, wherein the
glass mixing rod has a hexagonal cross-sectional shape that matches
a correspondingly shaped core of the center connector component for
proper alignment of the mixing rod with the optical fiber bundles
held in the respective connector inserts.
10. An optical fiber connector according to claim 8, wherein the
glass mixing rod has a glass core with an index of refraction that
closely matches that of the optical fibers to minimize reflections
at the interface between the connected bundles of optical
fibers.
11. An optical fiber connector according to claim 10, wherein the
glass mixing rod has an outer glass cladding of a low index of
refraction different from that of the glass core to provide an
optimum, light-transmissive aperture.
12. An optical fiber connector according to claim 11, wherein a
coating of optical gel is applied on the fiber ends of the optical
fiber bundles prior to being abutted on respective sides of the
glass mixing rod assembled in the center connector component.
13. An optical fiber connector according to claim 12, wherein the
optical gel is selected to have an index of refraction of about
1.46 to closely match that of a multimode optical fiber.
14. An optical fiber connector comprising a center component
provided with opposite first and second ends into which a first and
second connector insert is to be inserted, the first and second
connector inserts each holding ends of a respective optical fiber
bundle held in a respective ferrule; an optical core element
mounted in the center component having opposite ends against which
the ends of the respective optical fiber bundles in the first and
second connector inserts are to be abutted in alignment, wherein
the ferrules have a hexagonally shaped outer surface and the
connector inserts have a corresponding hexagonally shaped inner
cross-section; and fastener elements provided with the first and
second ends for securely holding the first and second connector
inserts.
15. An optical fiber connector according to claim 14, wherein said
opposite first and second ends of said center component have keyed
ends which match those of the connector inserts to be inserted
therein for holding them in rotational alignment with the center
component and with each other.
16. An optical fiber connector according to claim 15, wherein the
optical core element of the center component is a glass mixing rod
having a cross-sectional shape that matches a correspondingly
shaped cross-section of the center component for proper alignment
of the mixing rod with the optical fiber bundles in the connector
inserts.
17. An optical fiber connector according to claim 14, wherein the
center component, the first and second connector inserts and the
ferrules are made from a molded plastic material.
Description
TECHNICAL FIELD
The invention generally relates to a connector for optical fibers
for light transmission, and particularly to one having an
all-plastic optical fiber connector that provides for high levels
of light transmissivity to the output fibers.
BACKGROUND
Optical fibers are commonly used to transfer light over given spans
to provide illumination and for other light transmission
applications. Small-diameter fibers of standard fabrication size
are bundled in an array of fibers to deliver the desired optical
output, and connectors for the bundled fiber arrays are required
when the run of fibers has to span different sections or pieces of
equipment. Conventional connectors typically are made of metal and
consequently are bulky, heavy and costly. These typical connections
also require extreme care to align each end of the mating fibers
for efficient coupling of light across the connection. Existing
applications may require drilling holes through the connector
structures for retaining or anchoring them that may result in
making them more susceptible to corrosion compromising the strength
of the base structure. Another problem with existing types of
connectors that are commonly available is they do not provide a
high level of optical transmission or a uniform light distribution
across the interface between the ends of the optical fiber
bundles.
Accordingly, it is desirable to provide a connector for optical
fiber bundles that is small in size, light-weight, of low cost,
resistant to corrosion, and provides a high level of optical
transmission and uniform light distribution across the connector
interface.
SUMMARY OF INVENTION
In accordance with the present invention, an optical fiber
connector includes a first connector insert for holding exposed
ends of a bundle of optical fibers of a specified number packed in
a pre-determined packing pattern, a second connector insert for
similarly holding exposed ends of an opposite bundle of optical
fibers of the specified number packed in the pre-determined packing
pattern, and a center connector component having opposite first and
second ends into which the first and second connector inserts are
respectively inserted, and fasteners provided with the first and
second ends for securely holding the first and second connector
inserts in abutting contact with an optical core element in the
center connector component substantially in alignment with each
other in order to obtain a high level of optical transmission and
uniform light distribution across the interface between the
connected bundles of optical fibers.
In a preferred embodiment, the components of the optical fiber
connector are all made from molded plastic material. The connector
is designed with tight tolerances to provide minimal light loss.
The connector inserts have keyed ends that slot into
complementarily keyed ends of the center connector, and the
components are securely fastened together by fastener caps that
thread onto the opposing connector ends of the center connector
component. In a preferred example, the optical fibers are arranged
in a dense hexagonal packing pattern. A glass mixing rod with low
index of refraction cladding relative to the index of refraction of
the center core region is mounted within the center connector
component to provide an optimum, light-transmissive aperture. The
index of refraction of the center core region closely matches that
of the center core of the optical fibers to minimize reflections at
this interface. The bundled fiber ends are held in a dense packing
pattern in hex sleeves of the connector insert ends, and are coated
with optical gel to eliminate any air gap between optical elements
and inserted on respective sides of the mixing rod. The connector
is capable of evenly coupling, transmitting and distributing light
to each of the output fibers at an efficiency of about 65%.
Other objects, features, and advantages of the various embodiments
of the present invention will be explained in the following
detailed description with reference to the appended drawings.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is an assembly diagram illustrating an optical fiber
connector in accordance with an embodiment of the present
invention.
FIGS. 2A and 2B show the assembled optical fiber connector in
external and sectional views, respectively.
FIG. 3 illustrates a preferred example of a hex packing pattern for
an optical fiber bundle for use in the optical fiber connector
taken along view lines 3-3 in FIG. 2B.
FIG. 4 is a view in section of a mixing rod used in the center
connector component of the optical fiber connector taken along view
lines 4-4 in FIG. 2B.
DETAILED DESCRIPTION
In the following detailed description, certain preferred
embodiments are described as illustrations of the invention in a
specific application or physical environment in order to provide a
thorough understanding of the present invention. Those methods,
procedures, components, or functions which are commonly known to
persons of ordinary skill in the relevant art are not described in
detail as not to unnecessarily obscure a concise description
thereof. Certain specific embodiments or examples are given for
purposes of illustration only, and it will be recognized by one
skilled in the art that the present invention may be practiced in
other analogous applications or environments and/or with other
analogous or equivalent variations of the illustrative
embodiments.
Referring to FIG. 1, an embodiment of an optical fiber connector is
shown having a three component design of a first connector insert
10 for holding exposed ends of a bundle of optical fibers OB of a
specified number packed in a pre-determined packing pattern secured
in a ferrule 11, a second connector insert 20 for holding similarly
exposed ends of a corresponding bundle of optical fibers of the
specified number packed in the pre-determined packing pattern
secured in a ferrule 21, and a center connector component 30 for
optically connecting the ends of the fiber bundles of the two
connector inserts together. Each connector insert 10, 20 has a
keyed end 12, 22 that fits in slots of the complementarily keyed
ends 32a, 32b of the center connector component 30. A mixing rod 31
is assembled in the center connector component 30 and serves as an
optical interface for light transmission spanning the ends of the
two optical fiber bundles. The slotted fitting of the keyed ends of
the connector inserts results in the packed pattern of fibers of
each insert being held in a precise orientation in alignment with
each other in order to obtain a high level of optical transmission
and uniform light distribution across the interface between their
ends. The components of the optical fiber connector are preferably
all made from molded plastic material such as ULTEM, a high
temperature plastic. External fastener nuts 14, 24 are sleeved over
the barrel portions 13, 23 of the connector inserts 10, 20 are
threaded onto respective threadings 34a, 34b on the opposite ends
of the center connector component 30. A center hex lug 35 on the
center connector component 30 is provided for applying torque for
fastening and unfastening.
An assembled connector is shown in FIGS. 2A and 2B in external and
sectional views, respectively. The fiber ends of the optical fiber
bundles OB secured in their ferrules 11, 21 are abutted on each
side of the mixing rod 31 and held in alignment by the keyed ends
12, 22 of the connector inserts 10, 20. The fastener caps 14, 24
are fastened to the threadings 34a, 34b of the center connector
component 30 to securely hold the entire assembly together,
resulting in an optical connector assembly of slim profile. In a
preferred example of a 37-fiber bundle of 270 micron fibers, the
barrels 13, 23 of the connector inserts have diameters of 0.13
inch, and the center connector component has an outside diameter of
0.25 inch. The length spanning the fastener caps 14, 24 is 0.94
inch, and the length spanning the ends of the connector inserts 10,
20 is 1.55 inch. The length of the center connector component is
0.78 inch, and the length of the mixing rod 31 is 0.60 inch. The
assembly is designed for intimate contact and a close dimensional
fit between the fiber bundles and the center connector
component.
For light transmission applications, multimode optical fiber is
used. Multimode fiber is characterized by its ability to allow
numerous modes of light to be transmitted simultaneously. With a
large core diameter, multimode fiber is coupled easier then
single-mode fiber resulting in its wide use in variety of industry,
scientific and medical applications. An example of a multimode
fiber is APC 210/230/270 high OH fiber, available from Fiberguide
Industries, of Sterling, N.J. The fiber has a silica fiber core of
210 microns diameter, an intermediate plastic cladding of 230
microns diameter (10 microns thick), and an outer nylon jacket of
270 microns diameter (20 microns thick).
In FIG. 3, a preferred example of a packing pattern for a 37-fiber
bundle is shown. The fibers are bonded in the ferrules 11, 21 with
epoxy resin, then the optical faces of the potted fiber bundles are
optically ground and polished perpendicular to the long axis of the
connector sections. The ferrules have a hex cross-sectional shape
matching the inner cross-section of the connector inserts so that
they can be sleeved into the connector inserts in proper alignment.
37 optical fibers are arranged in a dense hexagonal packing
pattern, although other dense packing arrangements may be used. The
optical fibers are fabricated in a standard 270 micron size. The
nylon jacket is stripped off at the connector ends to allow for a
tighter packing factor, increasing the optical efficiency of the
connection. Other numbers of fiber bundles and packing patterns may
be used depending on the requirements of the light transmission
application. The optimum number of fibers, fiber size, and dense
packing arrangement are calculated according to well-known industry
formulas, such as those available in a Machinists Handbook or
through on line references such as Wikipedia. Reference is made to
such industry standard definitions for other examples of dense
packing patterns for optical fibers. The hexagonal packing pattern
is clamped and held in the ferrules 11, 21. When the connector
inserts are fitted into the slots of the keyed ends of the center
connector component, the fiber ends of the hex packing pattern are
held substantially in alignment with the corresponding fiber ends
of the other fiber bundle, thereby ensuring a high level of optical
transmission and uniform light distribution across the interface.
Tests results indicate that the connector is capable of evenly
transmitting in the range of about 65% of incoming broadband
light.
In FIG. 4, a view in section of a mixing rod used in the center
connector component is shown. The mixing rod 31 is hex-shaped (for
alignment) and made of glass material, and is mounted in the center
bore of the center connector component 30. This hex rod is allowed
to "free float" in center connector component 30 in order to
maintain intimate contact with connector inserts 10, 20 when
sandwiched in between them. The glass hex rod 31 has a low index of
refraction coating or cladding on its outer surface that provides
an optimum, light-transmissive aperture. The index of refraction of
the center core region closely matches that of the center core of
the optical fibers to minimize reflections at this interface. The
glass core and cladding index of refraction values are of different
values, defined to produce a hex rod with a 0.37 numerical aperture
to closely match that of the optical fibers being used. The center
connector component is designed with tight tolerances to provide
minimal light loss. An optically transmissive gel is applied on the
ends of the fiber bundles on each insert side, then the fiber ends
(with hex connector sleeve) are inserted into the end apertures on
each side of the glass hex rod until they abut each other. The
optical gel provides a light transmissive medium for contact
between the ends of the respective bundles. An example of a
suitable optical gel is one sold under the brand name Code 0608, by
Cargille Laboratories, Inc., New Jersey, which has an index of
refraction of about 1.46 to closely match that of the glass core of
a typical optical fiber.
The optical fiber connection of the present invention thus provides
a connector solution that is small in size, light-weight, of low
cost, and resistant to corrosion. The structure of the center
connector component and light-transmissive aperture ensures a high
level of optical transmission and uniform light distribution across
the connector interface. The complete assembly offers lower weight
for better payload, and all component parts can be injection-molded
for a lower cost product. The optical connector is unique in its
ability to take input light through any number of input fibers and
equally distribute this light to each of the output fibers,
regardless of the input to output fiber ratios.
Many modifications and variations may of course be devised given
the above description of the principles of the invention. It is
intended that all such modifications and variations be considered
as within the spirit and scope of this invention, as defined in the
following claims.
* * * * *